The present invention relates to non-hydrogenated canola oil having improved flavor and performance attributes especially suitable for food applications, and to the Brassica seeds, plant lines and progeny thereof from which the oil is derived.
Canola oil has the lowest level of saturated fatty acids of all vegetable oils. As consumers become more aware of the health impact of lipid nutrition, consumption of canola oil in the U.S. has increased. However, generic canola oil has limited use in deep frying operations, an important segment of the food processing industry, due to its instability. Canola oil extracted from natural and commercial varieties of rapeseed contains a relatively high (8%-10%) xcex1-linolenic acid content (C18:3) (ALA). The oil is unstable and easily oxidized during cooking, which in turn creates off-flavors of the oil and compromises the sensory characteristics of foods cooked in such oils. It also develops unacceptable off odors and rancid flavors during storage.
Hydrogenation can be used to improve performance attributes by lowering the amount of linoleic and xcex1-linolenic acids in the oil. In this process the oil increases in saturated and trans fatty acids, both undesirable when considering health implications. Blending of oil can also be used to reduce the xcex1-linolenic acid content and improve the performance attributes. Blending canola oil with other vegetable oils such as cottonseed will increase the saturated fatty acids content of the oil but decreases the healthy attributes of canola oil.
xcex1-Linolenic acid has been reported to oxidize faster than other fatty acids. Linoleic and xcex1-linolenic acids have been suggested as precursors to undesirable odor and flavor development in foods. To improve the functionality of canola oil, the University of Manitoba developed the canola variety xe2x80x9cStellarxe2x80x9d which has reduced xcex1-linolenic acid (Scarth et al., Can. J. Plant Sci., 68:509-511 (1988)). The low xcex1-linolenic acid oil was reduced in odor when heated in air, but still remained unacceptable to the sensory panel in flavor evaluations (Eskin et al., J. Am. Oil Chem. Soc. 66:1081-1084 (1989)). The oxidative stability of Stellar oil increased by 17.5% over the commercial variety Westar as measured by Active Oxygen Method (AOM) hours. (Can. J. Plant Sci. (1988) Vol. 68, pp. 509-511).
European Patent Application, EP 0 323 753 A1 describes a canola oil having an enhanced oleic acid content with increased heat stability in combination with other traits. The application further describes a frying oil with reduced xcex1-linolenic acid which imparts increased oxidative stability. No flavor and performance testing with the described oil was reported.
Data which shows that oxidative stability is not solely related to fatty acid composition (described below) indicates that increased stability cannot be inferred from fatty acid composition. The amount of xcex1-linolenic acid in the oil is only one factor which controls oxidative stability and flavor stability. Thus a canola oil which has improved stability in its flavor and performance attributes for use in food operations is needed. The present invention provides such an oil.
The present invention provides an oil comprising a non-hydrogenated canola oil having an oxidative stability of from about 37 to about 40 AOM hours in the absence of antioxidants. The oil of the present invention also has fry stability for up to at least 64 hours. After 64 hours of frying, the oil of the present invention has reduced total polar material content of about 23%, reduced free fatty acid content of about 0.7%, reduced red color developmentt as shown by a Lovibond color value of 6.7 red and reduced para-anisidine value of 125 absorbance/g. After 32 hours of frying, the oil of the present invention has reduced total polar material content of about 12%, reduced free fatty acid content of about 0.3%, reduced red color development as shown by a Lovibond color of 2.7 red and reduced para-anisidine value of 112 absorbance/g.
The present invention further provides a seed comprising a Brassica napus variety containing canola oil as described above, and progeny thereof.
The present invention further provides a plant line comprising a Brassica napus canola variety which produces canola oil as described above, and individual plants thereof.
Seed designated IMC 130 as described hereinafter was deposited on Apr. 16, 1993, with the American Type Culture Collection, Manassas, Virginia, and was assigned accession number 75446.
The present invention provides canola oil having superior stable flavor and performance attributes when compared to known canola oils. The invention also provides Brassica napus seeds, and plant lines producing seeds, from which such an oil can be produced.
A canola oil of the present invention is superior in oxidative stability and fry stability compared to known canola oils. The superior functionalities of the oil can be demonstrated, e.g., by standardized American Oil Chemists"" Society (AOCS) oil testing methods. The improved characteristics of the oil permit it to be used in new food products and permit the oil to be used without hydrogenation in situations where increased flavor stability, oxidative stability, fry stability and shelf-life stability are desirable.
In the context of this disclosure, a number of terms are used. As used herein, xe2x80x9cfunctionalityxe2x80x9d or xe2x80x9cperformance attributesxe2x80x9d means properties or characteristics of the canola oil and includes flavor stability, fry stability, oxidative stability, shelf-life stability, and photooxidative stability.
Oxidative stability relates to how easily components of an oil oxidize which creates off-flavors in the oil, and is measured by instrumental analysis using accelerated oxidation methods. American Oil Chemists"" Society Official Method Cd 12-57 for Fat Stability: Active Oxygen Method (re""vd 1989); Rancimat (Laubli, M. W. and Bruttel, P. A., JOACS 63:792-795 (1986)); Joyner, N. T. and J. E. McIntyre, Oil and Soap (1938) 15:184 (modification of the Schaal oven test). Oils with high oxidative stability are considered to be premium oils for shelf stable applications in foods, i.e., spray coating for breakfast cereals, cookies, crackers, fried foods such as french fries, and snack foods such as potato chips.
Fry stability relates to the resistance to degeneration of the oil during frying. Fry stability can be evaluated by measuring parameters such as total polar material content, free fatty acid content, color development and aldehyde generation. xe2x80x9cFry lifexe2x80x9d is determined by sequentially frying products in an oil and performing a sensory analysis of the flavor of the fried products. Fry life is measured as the length of time the oil is used for frying before the sensory analysis of a fried product degrades to a predetermined score. Oils for restaurants, hospitals and large institutions primarily are used for frying foods and require fry stability.
Flavor stability is determined by sensory analysis of an oil sample periodically taken from an oil held under defined conditions. For example, oils may be stored in an oven at an elevated temperature to accelerate the aging. The oil may also be stored at room temperature. However, the length of time required for testing renders this method to be less useful. Flavor stability is measured by the time it takes for the flavor of the oil to degrade to an established numerical score. The sensory panel rates the oil or food product from 1 (unacceptable) to 9 (bland). A rejection point is selected where the oil or food product begins to show deterioration. Bottled cooking oils and salad dressings require high flavor stability.
Photooxidative stability is determined from analysis of oil samples taken periodically from oil stored under defined light and temperature conditions. Photooxidative stability is reflected in the duration of time it takes for the flavor of the oil to degrade to a set score. Bottled cooking oils require high photooxidative stability.
Shelf-life stability is determined by the analysis of food samples cooked in the oil, then packaged and stored in an oven at an elevated temperature to accelerate aging. xe2x80x9cShelf-lifexe2x80x9d is the time it takes for the flavor of the food to degrade to give a set score. Oils for fried snacks require shelf-life stability.
As used herein, a xe2x80x9clinexe2x80x9d is a group of plants that display little or no genetic variation between individuals for at least one trait of interest. Such lines may be created by several generations of self-pollination and selection, or vegetative propagation from a single parent using tissue or cell culture techniques. As used herein, the terms xe2x80x9ccultivarxe2x80x9d and xe2x80x9cvarietyxe2x80x9d are synonymous and refer to a line which is used for commercial production.
xe2x80x9cSaturated fatty acidxe2x80x9d refers to the combined content of palmitic acid and stearic acid. xe2x80x9cPolyunsaturated fatty acidxe2x80x9d refers to the combined content of linoleic and xcex1-linolenic acids. The term xe2x80x9croom odorxe2x80x9d refers to the characteristic odor of heated oil as determined using the room-odor evaluation method described in Mounts (J. Am. Oil Chem. Soc., 56:659-663, 1979).
A xe2x80x9cpopulationxe2x80x9d is any group of individuals that share a common gene pool. The term xe2x80x9cprogenyxe2x80x9d as used herein means the plants and seeds of all subsequent generations resulting from a particular designated generation.
The term xe2x80x9cselfedxe2x80x9d as used herein means self pollinated.
xe2x80x9cGeneric canola oilxe2x80x9d refers to a composite blend of oils extracted from commercial varieties of rapeseed currently known, which varieties generally exhibited at a minimum 8-10% xcex1-linolenic acid content, a maximum of 2% erucic acid and a maximum of 30 xcexcmol/g total glucosinolate level. The seed from each growing region is graded and blended at the grain elevators to produce a uniform product. The blended seed is then crushed and refined, the resulting oil being a blend of varieties and sold for use. Table 1 shows the distribution of canola varieties seeded as percentage of all canola seeded in Western Canada in 1990. Canada is a leading producer and supplier of canola seed and oil.
xe2x80x9cCanolaxe2x80x9d refers to rapeseed (Brassica) which has an erucic acid (C22:1) content of at most 2 percent by weight based on the total fatty acid content of a seed, preferably at most 0.5 percent by weight and most preferably essentially 0 percent by weight and which produces, after crushing, an air-dried meal containing less than 30 micromoles (xcexcmol) per gram of defatted (oil-free) meal.
The term xe2x80x9ccanola oilxe2x80x9d is used herein to describe an oil derived from the seed of the genus Brassica with less than 2% of all fatty acids as erucic acid.
Genetic crosses are made with defined germplasm to produce the canola oil of the present invention having reduced polyunsaturated fatty acids, improved flavor stability, fry stability, oxidative stability, photooxidative stability and shelf-life stability, in a high yielding Spring canola background. IMC 129, a Spring canola variety with high oleic acid in the seed oil is crossed with IMC 01, a Spring canola variety with low xcex1-linolenic acid in the seed oil. Flower buds of the F1 hybrid are collected for microspore culture to produce a dihaploid population. The dihaploid plants (genetically homozygous) are selected with high oleic, and reduced linoleic and xcex1-linolenic acids in the seed oil and field tested for stability of the fatty acids and yield.
After five generations of testing in the field and greenhouse a high yielding selection with fatty acid stability in multiple environments is selected. Seed of selection is grown in isolation, harvested, and the oil extracted and processed to produce a refined, bleached and deodorized oil using known techniques. The oil produced was found to be functionally superior in oxidative stability and fry stability relative to a commercial-type, generic canola oil processed under similar conditions.
The canola oil of the present invention has an oxidative stability as determined by Active Oxygen Method (AOM) values of from about 35 to about 40 hours. This is significantly higher than any known pilot plant or commercial processed canola oil. The increase is 45 to 60% above commercial type generic canola oil.
Under extended frying conditions, canola oil of the invention is significantly lower than commercial-type generic canola in the oxidative tests for total polar material, free fatty acids, color development and p-anisidine value. The oil remains significantly lower in all oxidative parameters tested after 32 and 64 hours of frying.
The oil has about 12% and about 23% total polar materials at 32 and 64 hours of frying, respectively. This represents a 34% decrease at 32 hours and a 17% decrease at 64 hours compared to commercial type generic canola oil. The total polar materials are a measure of the total amount of secondary by-products generated from the triacylglycerols as a consequence of oxidations and hydrolysis, and their reduction indicates improved oxidative stability.
Oil of the invention has a reduced content of free fatty acids of about 0.3% and about 0.7% at 32 and 64 hours of frying, respectively. This represents a 37% decrease at 32 hours and a 23% decrease at 64 hours compared to commercial type generic canola oil. The level of free fatty acids is a measure of oxidation and hydrolysis of the triacylglycerols and their reduction also indicates improved oxidative stability.
The color developed in an oil during frying is also an indication of triacylglycerol oxidation. The oil of the present invention demonstrated a reduced level of color development. The Lovibond color is about 2.7 red and about 6.7 red at 32 and 64 hours of frying, respectively. This represents a 38% decrease at 32 hours and a 47% decrease at 64 hours compared to commercial type generic canola oil.
Reduced development of aldehydes during frying also indicate improved oxidative stability and are measured by the p-anisidine value in absorbance/g at 350 nm. The oil has a p-anisidine value of about 112 absorbance/g after 32 hours of frying and of about 125 absorbance/g after 64 hours of frying. This represents a 32% decrease at 32 hours and a 14% decrease at 64 hours compared to commercial type generic canola oil.
The oil additionally has improved oxidative stability and frying stability without hydrogenation or the addition of antioxidants. The improved oxidative and fry stability results in increased flavor stability of the oil. Addition of antioxidants to the oil will further increase oxidative stability.
Oil of the invention may be produced from, for example, a Brassica napus plant designated as IMC 130 or from a Brassica napus line designated as A13.30137. The seed oil has reduced amounts of total C16:0 (palmitic) and C18:0 (stearic) saturates of less than 6.5%, oleic acid from 74 to 80%, linoleic acid from 5 to 12%, xcex1-linolenic acid from 2.0 to 5.0% and erucic acid of less than 1%.
The oil of the present invention is especially suitable for use in food applications, in particular for frying foods, due to its superior oxidative stability and fry stability. Due to its non-hydrogenated nature, it is especially desirable for positive human health implications. The seeds, plant lines, and plants of the present invention are useful for the production of the non-hydrogenated canola of this invention.